The goal of this research is to develop the chemistry required for the construction of several conformationally restricted thyroliberin (TRH) analogs. The analogs are to be used to "map" the three dimensional requirements of TRH binding to its endocrine receptor site. After completition of the syntheses, biological testing, molecular modeling, and synthesis will be used interactively to design second and third generation analogs in the hope of optimizing biological activity.